The separate events reflect a new and potentially volatile pattern in Asian waters: As the Chinese government and the fast-modernizing naval branch of the People’s Liberation Army confidently extend the nation’s maritime reach, uneasy neighbors are tracking Chinese vessels, including military and maritime surveillance boats, fisheries law enforcement ships and fishing skiffs, and pushing back hard over anything deemed aggressive.

In recent weeks, Vietnam, the Philippines and Japan have all voiced concerns or made formal complaints over Chinese nautical movements. Some nations have deployed military ships or aircraft to disputed waters. The United States, the dominant military force in the Pacific, is watching closely and has sought to bolster its alliances with countries in the region.

The growing confidence of the Chinese navy is on open display. Here in the east coast port of Qingdao, host to an impressive naval review in 2009, destroyers and a submarine are docked for public viewing at a seaside military museum that extols the might of the navy. At another coastal city, Dalian, the navy has been rebuilding an ex-Soviet aircraft carrier, the Varyag, which is expected to be operational this year.

American officials have said one of the Chinese navy’s main goals in modernizing is to operate in an area where the United States currently has naval supremacy: the waters of the western Pacific that lie beyond Japan, Taiwan and the Philippines, what is commonly known as the “first island chain.” .